From cd445165c50a46042e0cf17eb0081879f9cf4d52 Mon Sep 17 00:00:00 2001
From: Emil Fresk <emil.fresk@gmail.com>
Date: Tue, 17 May 2022 20:12:36 +0200
Subject: [PATCH] More ergonomic error from static asserts messages

---
 macros/src/codegen/pre_init.rs   | 25 ++++++++++++++++++++++---
 ui/task-priority-too-high.stderr | 14 +++++++++++---
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/macros/src/codegen/pre_init.rs b/macros/src/codegen/pre_init.rs
index 91c9991274b4..ae2fd0503fae 100644
--- a/macros/src/codegen/pre_init.rs
+++ b/macros/src/codegen/pre_init.rs
@@ -49,8 +49,14 @@ pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream
             Some((&task.args.priority, &task.args.binds))
         }
     })) {
+        let es = format!(
+            "Maximum priority used by interrupt vector '{}' is more than supported by hardware",
+            name
+        );
         // Compile time assert that this priority is supported by the device
-        stmts.push(quote!(let _ = [(); ((1 << #nvic_prio_bits) - #priority as usize)];));
+        stmts.push(quote!(
+            const _: () = assert!((1 << #nvic_prio_bits) >= #priority as usize, #es);
+        ));
 
         stmts.push(quote!(
             core.NVIC.set_priority(
@@ -72,8 +78,14 @@ pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream
             None
         }
     }) {
+        let es = format!(
+            "Maximum priority used by interrupt vector '{}' is more than supported by hardware",
+            name
+        );
         // Compile time assert that this priority is supported by the device
-        stmts.push(quote!(let _ = [(); ((1 << #nvic_prio_bits) - #priority as usize)];));
+        stmts.push(quote!(
+            const _: () = assert!((1 << #nvic_prio_bits) >= #priority as usize, #es);
+        ));
 
         stmts.push(quote!(core.SCB.set_priority(
             rtic::export::SystemHandler::#name,
@@ -90,8 +102,15 @@ pub fn codegen(app: &App, analysis: &Analysis, extra: &Extra) -> Vec<TokenStream
         };
         let binds = &monotonic.args.binds;
 
+        let name = &monotonic.ident;
+        let es = format!(
+            "Maximum priority used by monotonic '{}' is more than supported by hardware",
+            name
+        );
         // Compile time assert that this priority is supported by the device
-        stmts.push(quote!(let _ = [(); ((1 << #nvic_prio_bits) - #priority as usize)];));
+        stmts.push(quote!(
+            const _: () = assert!((1 << #nvic_prio_bits) >= #priority as usize, #es);
+        ));
 
         let mono_type = &monotonic.ty;
 
diff --git a/ui/task-priority-too-high.stderr b/ui/task-priority-too-high.stderr
index e0978f718860..a5ce918a4c92 100644
--- a/ui/task-priority-too-high.stderr
+++ b/ui/task-priority-too-high.stderr
@@ -1,7 +1,15 @@
+warning: unused variable: `cx`
+  --> ui/task-priority-too-high.rs:12:13
+   |
+12 |     fn init(cx: init::Context) -> (Shared, Local, init::Monotonics) {
+   |             ^^ help: if this is intentional, prefix it with an underscore: `_cx`
+   |
+   = note: `#[warn(unused_variables)]` on by default
+
 error[E0080]: evaluation of constant value failed
- --> $DIR/task-priority-too-high.rs:3:1
+ --> ui/task-priority-too-high.rs:3:1
   |
 3 | #[rtic::app(device = lm3s6965)]
-  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ attempt to compute `8_usize - 9_usize`, which would overflow
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'Maximum priority used by interrupt vector 'I2C0' is more than supported by hardware', $DIR/ui/task-priority-too-high.rs:3:1
   |
-  = note: this error originates in the attribute macro `rtic::app` (in Nightly builds, run with -Z macro-backtrace for more info)
+  = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)